The present invention relates to a liquid ejection head in which a chamber formation plate is worked by forging, and to a method of manufacturing such a liquid ejection head.
Forging work is used in various fields of products. For example, it is thought that a pressure generating chamber of a liquid ejection head is molded by forging metal material. The liquid ejection head ejects pressurized liquid from a nozzle orifice as a liquid droplet, and the heads for various liquids have been known. An ink jet recording head is representative of the liquid ejection head. Here, the related art will be described with the ink jet recording head as an example.
An ink jet recording head (hereinafter, referred to as “recording head”) used as an example of a liquid ejection head is provided with a plurality of series of flow paths reaching nozzle orifices from a common ink reservoir via pressure generating chambers in correspondence with the orifices. Further, the respective pressure generating chambers need to form by a fine pitch in correspondence with a recording density to meet a request of downsizing. Therefore, a wall thickness of a partition wall for partitioning contiguous ones of the pressure generating chambers is extremely thinned. Further, an ink supply port for communicating the pressure generating chamber and the common ink reservoir is more narrowed than the pressure generating chamber in a flow path width thereof in order to use ink pressure at inside of the pressure generating chamber efficiently for ejection of ink drops.
According to a related-art recording head, a silicon substrate is preferably used in view of fabricating the pressure generating chamber and the ink supply port having such small-sized shapes with excellent dimensional accuracy. That is, a crystal surface is exposed by anisotropic etching of silicon and the pressure generating chamber or the ink supply port is formed to partition by the crystal surface.
Further, a nozzle plate formed with the nozzle orifice is fabricated by a metal board from a request of workability or the like. Further, a diaphragm portion for changing a volume of the pressure generating chamber is formed into an elastic plate. The elastic plate is of a two-layer structure constituted by pasting together a resin film onto a supporting plate made of a metal and is fabricated by removing a portion of the supporting plate in correspondence with the pressure generating chamber.
Meanwhile, according to the above-described related-art recording head, since a difference between linear expansion rates of silicon and the metal is large, in pasting together respective members of the silicon board, the nozzle plate and the elastic plate, it is necessary to adhere the respective members by taking a long time period under relatively low temperature. Therefore, enhancement of productivity is difficult to achieve to bring about a factor of increasing fabrication cost. Therefore, there has been tried to form the pressure generating chamber at the board made of the metal by plastic working, however, the working is difficult since the pressure generating chamber is extremely small and the flow path width of the ink supply port needs to be narrower than the pressure generating chamber to thereby pose a problem that improvement of production efficiency is difficult to achieve.
In these circumstances, a problem intrinsic to forging must be solved. That is, a relative position between a mother plate and a forging die must be accurately set, and if this relative position is shifted, a worked region in which groove-shaped recesses to be pressure generating chambers are press-molded is not positioned accurately on the mother plate. Accordingly, assembling accuracy at the time when a chamber formation plate is assembled as a flow path unit is lowered, and in an extreme case, there is an anxiety that a problem arises in the ejection performance of ink droplets
Since the correct relative position between the mother plate and the forging die has the important role as described above, a reference hole for receiving a reference pin raised from the forging die is bored in the mother plate, and the reference pin is inserted in the reference hole so that the relative position between the mother plate and the forging die is determined.
However, when the plastic working is performed to the worked region, a plastic flow occurs in the mother plate, and there is an anxiety that the reference hole is deformed or its position is shifted by the displacement of a raw material occurring at this time. If such deformation or shift of the position occurs, the forming position of the pressure generating chamber is shifted, and a bad influence is exerted upon the assembly quality of a flow path unit and ejection performance. Alternatively, in a case where the forging die is arranged in a progressive style, there arises a problem that when the mother plate is transferred to a forging die of a next working stage, a reference pin provided in a die at that stage and the reference hole are not normally coincident with each other.